RFR: 8262520: Add SA Command Line Debugger support to connect to debug server [v6]

[Yasumasa Suenaga]

> `attach` command on CLHSDB supports to attach live process (PID) and coredump, but it cannot connect to debug server. CLHSDB does not have a command to connect to debug server.
> 
> Other jhsdb commands (jstack, jmap, etc...) can connect debug server via `--connect` option, so CLHSDB should connect to it.
> 
> After this change, you can connect to debug server with 'connect <hostname>'.

Yasumasa Suenaga has updated the pull request incrementally with one additional commit since the last revision:

  Add assertion to check unexpected exceptions are happened in command line debugger

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2773/files
  - new: https://git.openjdk.java.net/jdk/pull/2773/files/59d2dd00..4f1cd7e9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2773&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2773&range=04-05

  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2773.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2773/head:pull/2773

PR: https://git.openjdk.java.net/jdk/pull/2773